Underage drinking continues to be a major public health problem, affecting the lives of adolescents, young adults and their families, and exacting a huge toll on the nation socially and economically. This R03 application addresses two important, yet highly understudied aspects of the underage drinking problem, both of which are related to alcohol availability: false ID use and the provision of alcohol to minors. The proposed research involves analysis of existing data collected as part of the investigative team's longitudinal prospective study of 1253 young adults who were originally sampled as incoming college students. By their third year of college (ages 19 to 21), 60% of participants had used a falsified form of identification (false ID) to obtain alcohol, and, two years later, 44% did not see any problem with providing alcohol to someone between the ages of 18 to 20 years old. The study has three aims. First, we will identify personal and environmental risk factors that predict the use of a false ID to obtain alcohol during college. Second, because of the widespread availability of alcohol, it is unclear what (if any) additional risk for problematic drinking might be incurred by using a false ID; therefore, the second aim of this study will be to understand to what extent false ID use might exacerbate the development of an alcohol use disorder (AUD). Specifically, we will attempt to isolate the drinking patterns that can be attributed to false ID use, adjusting for demographics, fraternity/sorority involvement, and other known risk factors for problematic drinking in college students. Third, we will identify risk factors for the provision to alcohol to minors by peers who have recently attained legal age to purchase alcohol. Here we will examine the possible role of perceived legal and health risks of providing alcohol to a minor. Clearly, this group of young, legal-age adults is a potential target for prevention activities, and this application aims to provide information that could be used to design a new set of prevention strategies for reducing the availability of alcohol to underage drinkers via their legal-age peers. This application uniquely combines cutting-edge statistical methodology (e.g., latent variable modeling) with a practical focus on translational research that can lead to policy recommendations to reduce underage drinking. The knowledge gained in this study could be potentially useful for parents, who need better information about the potential for false ID use and could be encouraged to have conversations with their legal-age children about why it is important to refrain from supplying alcohol to minors-including their younger siblings-for both legal and health reasons. Importantly, the impact of this research extends beyond college campuses. Colleges and communities must implement comprehensive strategies that target different aspects of the underage drinking problem, from screening, identification, and referral of high-risk drinkers, to implementing policies that curb availability. To this end, we are committed to translating our scientific findings for that very purpose through our continued collaborations with policy makers, college officials, parents, and student groups.